Heretofore, well casing hangers for suspending an inner string of well casing have utilized so-called locking rings which are continuously urged outwardly and fit in receiving grooves in the inner wall of an outer casing string. Such locking rings have also employed releasable retaining means which are sheared by the weight of the inner pipe string when the inner pipe string is accurately positioned relative to the outer casing string and thereby permits the locking ring to be locked outwardly in the receiving grooves so that the ring may not be inadvertently moved inwardly to release the inner pipe string.
Such prior art devices, such as shown in U.S. Pat. No. 3,893,717 dated July 8, 1975 and U.S. Pat. No. 3,420,308 dated Jan. 7, 1969, have usually utilized either a separate spring element inside or behind the locking ring to urge the ring outwardly, or a one-piece integral ring split longitudinally which continuously expands outwardly. Separate shear rings held in position by shear pins which shear at a predetermined pipe load have been utilized heretofore for the releasable retaining means.
While the above type hangers operate satisfactorily, the use of separate spring elements increases the number of parts which increases the possibility of malfunctioning. Further, the use of a separate shear ring which is separately secured by a plurality of shear pins is time consuming in positioning on the inner pipe string and engages the locking ring in abutting relation only when the locking ring expands outwardly.